Reevaluating the antiquity of the Palmrose site: Collections-based research of an early plank house on the northern Oregon Coast

Large-scale excavations conducted by Smithsonian Institution archaeologists and avocational archaeologists during the 1960s and 1970s at three sites in Seaside, Oregon, resulted in the recovery of a diverse range of material culture curated by multiple institutions. One site, known as Palmrose (35CLT47), provides compelling evidence for the presence of one of the earliest examples of a rectangular plank house along the Oregon Coast. Previous research suggests habitation of the Palmrose site occurred between 2340 cal BC to cal AD 640. However, recent research highlights significant chronometric hygiene concerns of previously reported radiocarbon dates for the Seaside area, calling into question broader regional chronologies. This paper presents a revised chronology for the Palmrose site based on 12 new accelerator mass spectrometry (AMS) radiocarbon dates of ancient cervid bones. I evaluate these new dates and previously reported radiocarbon dates from the site, applying chronometric hygiene assessments and Bayesian statistics to build a refined chronology for the Palmrose site. Calibration of the 12 AMS radiocarbon dates suggests an initial occupation range from 345−55 cal BC and a terminal occupation range from cal AD 225−340−. Bayesian modeling of the Palmrose sequence suggests initial occupation may have spanned from 195−50 cal BC and the terminal occupation from cal AD 210−255. Modeling suggests the maximum range of occupation may span from 580−55 cal BC to cal AD 210−300 based on the start and end boundary calculations. Bayesian modeling of radiocarbon dates directly associated with the plank house deposits suggests the plank house’s occupation may have spanned from 160−1 cal BC to cal AD 170−320. The new radiocarbon dates significantly constrain the Palmrose habitation and alter regional chronologies.